It is well know that some people have problems with one or more joints in their feet. Examples of problems include a rigid or limited range of motion in one or more joints, painful rheumatoid arthritis in one or more joints, deformed bones associated with arthritis, and/or unstable or painful joints from previous surgeries.
Several procedures have been developed to treat these conditions. For example, intra-articular soft tissue procedures, arthrodesis, and Keller arthroplasty have been developed for the first metatarsal phalangeal joint. An intra-articular soft tissue procedure involves reconstructing the joint utilizing soft tissue structures within and around the joint. An arthrodesis procedure involves the fusion of the bones of the joint. A Keller arthroplasty procedure involves the reconstruction of the joint after removal of a portion of the bone from the joint.
Unfortunately, none of these procedures or treatments is completely satisfactory. For example, intra-articular soft tissue procedures are successful for only a limited range of patients. Arthrodesis is effective in eliminating pain but at the expense of joint immobility, load transfer complications, and limited shoe wear options. Keller arthroplasty frequently relieves pain but sometimes results in an unstable toe and loss of toe purchase due to muscle weakness and imbalance.
An alternate solution to the problem includes the use of a double stemmed implant to combat the destructive processes in the joints of the foot. One type of implant 10P is illustrated in FIGS. 1A and 1B. In particular, FIG. 1A illustrates the implant 10P in a relaxed condition, while FIG. 1B illustrates the implant 10P (partly in phantom) positioned in a first metatarsal phalangeal joint 12P of a great toe 14P. In FIG. 1B, the toe 14P is flexed. Additionally, the sesamoid apparatus 15P is illustrated in FIG. 1B.
The implant 10P includes a proximal stem 16P, a distal stem 18P, a hinge 20P and a pair of metal grommets 22P. The proximal stem 16P is inserted into the metatarsal 24P while the distal stem 18P is inserted into the proximal phalanx 26P. The implant 10P is designed to flex at the center of the hinge 20P. The grommets 22P are positioned on opposite sides to the hinge 20P. The implant 10P is sold by Wright Medical Technology, Inc. located in Arlington, Tenn., under the trademark "SWANSON.RTM.".
Unfortunately, the results obtained with the implant 10P illustrated in FIGS. 1A and 1B are not entirely satisfactory. More specifically, the implant 10P must deform to accommodate the anatomy of the first metatarsal phalangeal joint 12P. As a result thereof, the implant 10P limits the range of motion of the joint 12P, increases the stress at the joint 12P and/or alters the normal flexing of the toe 14P.
Further, the deformation of the implant 10P can cause binding in the joint 12P. Moreover, referring to FIG. 1B, the grommets 22P can contact during flexing of the toe 14P.
Furthermore, the cuts to metatarsal 24P and/or the proximal phalanx 26P required to make space for the implant 10P can interfere with the sesamoid apparatus 15P or the flexor hallucis brevis attachment (not illustrated in FIG. 1B). This can significantly influence how the toe 14P functions with the implant 1OP.
In light of the above, it is an object of the present invention to provide a toe implant for the first metatarsal phalangeal joint for the great toe that provides increased available range of motion. Another object of the present invention is to provide a toe implant that allows the toe to move in a fashion that better simulates the natural motion of the first metatarsal phalangeal joint. Still another object of the present invention is to provide a toe implant that does not significantly increase the stress at the joint or alter the normal flexing of the toe. Yet another object of the present invention is to provide a toe implant that does not interfere with the sesamoid apparatus or the flexor hallucis brevis attachment. Another object is to provide a toe implant that provides relatively good joint mobility, relatively good load transfer, relatively good toe stability, and relatively good toe purchase. Still another object is to provide a toe implant that is relatively easy to insert into the first metatarsal phalangeal joint.